1. Field of the Invention
The present invention relates to an engine exhaust apparatus haVing a muffler or a silencer which eliminates exhaust gas noises.
2. Description of the Prior Art
In order to reduce sounds of exhaust gases from an engine, a muffler or a silencer is connected to an exhaust passageway. The sounds or noises of exhaust gases generated from the engine are generally known to be reduced by passage of the exhaust gases through a plurality of small holes of an elimination chamber so that the gases interact to lower their sound level. Such a principle has been used as shown, for example, in Japanese Utility Model Laid-open application Ser. No. 62-90916.
On the other hand, in Japanese Utility Model Laid-open application Ser. No. 60-128925, there is disclosed a muffler which has a front expansion chamber and a rear expansion chamber. The front end of the muffler and the rear expansion chamber are connected by an inlet pipe bypassing the front expansion chamber and the rear end of the muffler and the front expansion chamber are connected by an outlet pipe bypassing the rear expansion chamber. Further, there are provided a plurality of small holes in the inlet pipe at the portion which faces the front expansion chamber and a plurality of small holes in the outlet pipe at the portion which faces the rear expansion chamber.
In such a muffler, exhaust gases introduced into the inlet pipe are expanded by partly entering into the front expansion chamber through the plurality of small holes in the inlet pipe and partly entering into the rear expansion chamber from the rear end of the inlet pipe. Then, exhaust gases in the front expansion chamber are emitted to the outside through the outlet pipe and exhaust gases in the rear expansion chamber are delivered into the outlet pipe through the plurality of small holes in the outlet pipe and then emitted to the outside through the outlet pipe.
According to the above described muffler, since the outlet pipe has a plurality of small holes, the sound of exhaust gases delivered from the front expansion chamber into the outlet pipe and the sound of exhaust -gases delivered from the rear expansion chamber into the outlet pipe through the plurality of small holes interact properly to suppress noise so as to lower resonance phenomenon in the outlet pipe. The length of pipe can thereby be shortened.
Furthermore, Japanese Utility Model Laid-open application Ser. No. 60-92715 discloses a silencer which has a sound absorber surrounding a pipe with a plurality of small holes therein in order to suppress high frequency sounds. However, the above-described silencers have no structural features to positively create comfortable or sporty sounds as well as to suppress the magnitude of exhaust sounds by combining well-known elements such as a pipe having a plurality of small holes or a sound absorber.